1. Field of the Invention
The present invention relates to an inlet manifold for internal combustion engines functioning on the principle of Otto-engine or diesel-engine.
2. Discussion of the Prior Art
It is known that internal combustion engines feature, on the intake side, inlet manifolds for transportation and distribution of air and fuel mixtures. Depending on the arrangement of the component and the preparation of the fuel-air mixture, the inlet manifolds may be intake manifolds, collector tanks, intake passages, intake pipes, collector intake pipes, collectors and individual intake runners, oscillatory intake passages, intake runners, resonance chambers and resonance intake pipes, variable-configuration intake manifolds and systems with variable-tract intake manifolds etc.
Known inlet manifolds such as the intake channel of a variable-configuration intake manifold according to DE-A 195 04 256 are made of polyamides. Generally known are also inlet manifolds of cast metal. In general, inlet manifolds are made by sand casting metal or are made of plastic, in each case using the lost-wax core principle. These parts and the methods of manufacture exhibit disadvantages. Sand casting results in components with widely varying wall thickness e.g. with thickness limits of 2.5 to 4.5 mm. Consequently, castings are heavy and the surfaces are rough. Rough inner surfaces impair the flow behaviour of the fluids passing through the component, rough outer surfaces are detrimental to the appearance and haptic of the part. Also, residual amounts of the shape-forming core may remain in the component, and the component may have to be worked further by chipforming processes. Some of these disadvantages may be overcome by using plastics. However, because of the ever increasing thermal load on engine components it is necessary to employ suitably heat-resistant plastics. These heat-resistant plastics are expensive and e.g. polyamides which are particularly suitable are difficult to recycle.